GB2296280A - Multiple glazing unit with peripheral support member - Google Patents

Abstract

A multiple glazing unit comprises two vitreous material panels 1, 2 positioned in face-to-face spaced apart relationship. A gas space 3 therebetween is delimited by a peripherally extending spacer 4. A cordon of resin 9 secures the panels together. At least one portion 1a of the first vitreous panel 1 overlaps an edge 2a of the second vitreous panel 2. At least one support member 7, extending along at least the major part of one margin of the glazing unit, is secured to the vitreous panels by the resin 9 to constitute means for fixing the glazing unit to a support structure. The resistance of the unit to forces which may arise during transport and installation of the unit is substantially improved. <IMAGE>

Description

A MULTIPLE GLAZING UNIT AND METHOD FOR ITS CONSTRUCTION The present invention relates to a multiple glazing unit, in particular to such a unit comprising two vitreous material panels positioned in face-to-face spaced apart relationship, having a gas space there-between delimited by a peripherally extending spacer. The present invention also relates to a method for constructing such a unit.

Multiple glazing units, for example double glazing units, are very useful for increasing thermal and sound insulation of the interior of buildings and therefore for increasing the comfort of the occupants of the building compared to the feeble insulation provided by ordinary simple glazing units.

Simple double glazing units are constituted by two sheets of vitreous material such as glass fixed and maintained in a spaced relationship one to the other, usually at their edges, by the intervention of a spacer. The spacer is usually a metallic profile which is adhered to the sheets, along the length of the four edges thereof. An hermetically sealed hollow space is formed between the sheets, delimited by the spacer. This space is filled with a dry gas such as dry air. It is important that the gas confined within the space should be maintained in a dry state in order to avoid any condensation of water at the interior of the double glazing during changes in temperature. If there is condensation of water vapour on the internal walls of the sheets, the transparency of the glazing will be reduced and the visibility through the glazing will be affected.

A multiple glazing unit is known comprising two vitreous material panels positioned in face-to-face spaced apart relationship. A gas space between the panels is delimited by a peripherally extending spacer. A cordon of resin extends at least between the spacer and each of the panels to hold the panels in place. Usually, the unit is mounted in a frame of U-sectioned profile in which the edges of the panel are retained, this frame then being fixed to a support structure, for example, within the opening in the wall of a building.

The commercial demand is more and more to install the glazing units in bays by adhesively securing the panels to the support structure instead of mounting the panels in a U-section profile frame. This recent technique of panel installation is often referred to as "exterior panel adhesive fixing" or (somewhat improperly) as structural glazing". This technique allows one to form facades which appear to be totally glazed. It also allows one to install the units in a flush manner with the body-work of a vehicle for example. This technique allows one to obtain advantageous aesthetic effects.

French patent application FR-A-2638476 describes a system for fixing a double glazing unit to a support structure of a building by the "structural glazing" technique mentioned above. The double glazing unit is secured, by one of its panels, to an intermediate profile which is then placed in a metal frame fixed to the structure of the building. This arrangement is relatively complicated and onerous and it is found that the integrity of the installed multiple glazing unit and its fixing to the structure of the building cannot necessarily be guaranteed.

It is an object of the present invention to provide a multiple glazing unit ready to be easily mounted by reliable fixing means to the support structure intended to receive it according to the "structural glazing" mounting technique described above.

It is a further object of the present invention to provide a simple method for the construction of a multiple glazing unit, which method is capable of producing the unit in a ready-to-install condition, requiring substantially no further construction on site, other than securing of the unit to the support structure of a building for example.

We have surprisingly discovered that these objects can be achieved where the construction of the unit is such that at least one portion of the first panel overlaps an edge of the second panel and the resin used to secure both panels also secures at the same time at least one support member for fixing the unit to the support structure of the building or to the chassis of a vehicle or the like.

Thus, according to a first aspect of the invention, there is provided a multiple glazing unit comprising at least two vitreous material panels positioned in face-to-face spaced apart relationship, having a gas space therebetween delimited by a peripherally extending spacer, and a cordon of resin securing the panels together, wherein: - at least one portion of the first of the panels overlaps an edge of the second of the panels; and - at least one support member extending along at least the major part of one margin of the glazing unit is secured to the vitreous panels by the resin to constitute means for fixing the glazing unit to a support structure.

According to a second aspect of the invention, there is provided a glazed structure, such as a building, at least one facade of which incorporates a plurality of glazing units as defined above.

It is important that the resin serves not only to secure the panels together but also to secure the support member or members to the panels, in what may be described as a monolithic structure. Furthermore, the invention provides a multiple glazing unit which is ready for installation by a structural glazing technique and which may be easily constructed in a factory with carefully controlled application of the resin.

It is indeed surprising to the man skilled in the art, that the two functions of securing the panels together and securing the panels to one or more support members can be performed by one and the same material without detriment to either function.

It is a characteristic of the present invention that at least one portion of one of the vitreous panels overlaps an edge of the other of the vitreous panels, the overlapping marginal portion preferably extending around the periphery of the unit. This can be achieved when the two panels of the double glazing unit have different dimensions.

In order to provide the greatest rigidity to the spacer / panels / support member assembly, the cordon of resin preferably extends at least between the spacer and each of the panels and especially is in contact with at least one face of the first panel and with at least one face of the second panel, and is ideally also in contact with the overlapped edge of the second panel. The overlapping characteristic of the panels enables the resin to contact with a face and an edge of at least one of the panels, providing a highly resistant bond, substantially improving the resistance of the unit to forces which may arise, for example, during use.

Preferably, the resin is an adhesive material which exhibits, at 200C, an elongation of not more than 12.5% when subjected to a tensile stress of 0.1 MPa, advantageously 0.14 MPa, as measured according to ISO 8339. The adhesive material preferably also exhibits, at 200C, an elongation of not more than 12.5% when subjected to a tensile stress of 0.1 MPa after ageing for 500 hours in water at 550C, especially when subjected to a tensile stress of 0.14 MPa after ageing in water for 1000 hours at 450C. We mostly prefer that the adhesive material exhibits an elongation of not more than 12.5% when subjected to a tensile stress of 0.1 MPa, preferably of 0.14 MPa over a temperature range of -200C to 55qC, preferably over a temperature range of -400C to 700C.

We prefer that the adhesive material exhibits a rupture strength at 200C of more than 0.70 MPa, preferably at least 0.84 MPa, and a deformation at rupture of greater than 50%. The most preferred adhesive material exhibits cohesive rupture when subjected to a tensile stress in excess of the rupture strength thereof.

Preferably, the adhesive material is selected from silicone adhesive materials, but polysulphide and polyurethane adhesive materials may also be used. When a polysulphide or other light sensitive material is used, it is preferred to include in the glazing unit means to shield the adhesive material from sunlight. Such means may comprise, for example, a UV shield coating on the exterior sheet of vitreous material or a band of vitreous enamel formed by silk-screen printing.

The spacer plays the essential role of maintaining a predetermined distance between the two vitreous panels.

It should in particular be relatively resistant to deformation, in order to support forces, derived for examples from the action of wind, whilst avoiding too high a variation in the spacing between the panels. To achieve this, the spacer has a high transverse rigidity.

If the spacer is formed of a polymer material or other deformable material, it should preferably include a rigid element to limit its deformation, at least in the transverse direction. The "cordon of resin" has inter alia the role of securely holding the two panels in position against the spacer. The combination of these two elements provides a multiple glazed unit of high quality, the properties of which remain substantially constant in use.

Preferably, layers of sealant are positioned between the spacer and each of the panels. Thus, a water tight joint may be achieved with the aid of two different materials.

The first material, which is highly water impermeable, but relatively flexible, is referred to generally herein as a "sealant", and may for example be a polyisobutylene.

The second material which is highly adhesive and relatively rigid, is referred to generally herein as the resin In a preferred embodiment, at least part of each face of the spacer in contact with the sealant extends obliquely with respect to the inner surface of the adjacent panel, such that the layer of sealant in contact therewith extends progressively from a region of minimum thickness to a region of maximum thickness, the resin being in contact with the sealant substantially in the region of maximum thickness.

This particular form of spacer is favourable to improving the life expectancy of the glazing and also improves the thermal isolation because for a given level of water vapour penetration, the thermal bridge generated by the spacer at the edges of the glazing unit is reduced.

By arranging for the sealant to have a region of minimum thickness, the distance between the spacer and the sheets will be a minimum in this region, and may even be lower than that conventionally used and may be less than 1.0 mm, preferably not greater than 0.5 mm, most preferably not greater than 0.2 mm.

The smaller the distance between the sheets and the spacer in this region of minimum thickness, the narrower is the access pathway that the humidity must pass through in order to penetrate into the gas space of the glazing unit. This characteristic consequently enables the sealing of the internal space of the unit. Preferably this distance should be as small as possible and may at the limit be zero. However, it is best to avoid direct contact between the spacer and the sheets of glass, if the spacer is metallic, since this would among other things provide an unfavourable thermal isolation.

The spacer may be formed of a metal or of a plastics material. The spacer may be hollow, the hollow interior of the spacer being in gas communication with the gas space. When the hollow interior of the spacer is in gas communication with the gas space, a desiccant may be located in the hollow interior. Such a spacer may have a trapezium shaped cross-section.

Alternatively, the spacer has a cross-section which may be open to the gas space. For example, the cross-section of the spacer has a flared "U" shape. Such a crosssection may comprise two flared arm portions interconnected by a base portion. The flared arm portions may be deformably connected to the base portion to enable some flexibility of the cross-sectional shape of the spacer which serves to take up some of the stresses that result from temperature increases or other causes. In these embodiments, a desiccant may be located within the spacer. Alternatively or additionally, the sealant may contain a desiccant.

In another embodiment, the spacer is essentially formed by a polymeric material. A suitable spacer is known as a "Swiggle Strip" (Trade Mark) ex TREMCO SA, of F-75643 Paris, Cedex 13, which is a pre-extruded butyl ribbon having a metal core and containing a molecular sieve desiccant powder. The spacer acts additionally as a moisture barrier.

While it is possible for a number of support members to be provided, which together extend along at least the major part of one margin of the glazing unit, it is preferred that a single support member be provided, in the form of a rigid supporting frame which extends substantially fully around the periphery of the unit.

This has the advantage of providing the best fixation of the glazing unit to the carrying structure. The frame may be formed of aluminium, stainless steel or a rigid plastics material such as PVC. The frame may be provided with means whereby it is to be fixed to the support structure of a building or the like, such means including, for example, suitably positioned and shaped flanges, brackets, lugs and fixing holes. The glazing panels are secured directly to the frame with the aid of the adhesive material. Any space between the adjacent vitreous panels and the frame is preferably filled with a sealant material, such as a silicone material having a low modulus of elasticity, acting to seal the glazing unit as a whole from the ingress of moisture.

To enable the glazing unit according to the invention to be mounted using a "structural glazing" technique, it is preferred that the support members(s) do not extend beyond the plane of that vitreous sheet of the unit which is intended to be placed in the exterior position when the unit is assembled, together with others, in a structure such as a building.

A glazing panel which consists of or includes a pair of vitreous sheets adherent to an intervening layer of polymeric material, is referred to herein as a composite panel. It is peferred that one of the vitreous panels of the glazing unit according to the invention is constituted by a composite glazing panel having a pair of vitreous sheets adhered to an intervening layer of polymeric material sandwiched there-between. The intervening polymeric layer may be selected from polyesters, vinyl polymers, epoxy resins, and acrylic resins or PVB.

The nature of the polymeric material for forming the inter layer is of considerable importance for the performance of the composite panel. There are a number of materials which have the required properties and could in fact be used. For safety purposes, PVB is an example of suitable material for the intervening polymer material. Other suitable intervening polymeric layer materials are selected from polyesters, vinyl polymers, epoxy resins, and especially acrylic resins. Such materials afford a number of polymers having exceptional acoustic properties. References to acoustic properties of composite panels throughout this specification are references to such properties measured in accordance with the German Federal Republic Standard VDI 2.719. For a given desired level of acoustic insulation, the use of such a polymer can allow a significant reduction in the thickness and thus in the weight of vitreous material which has to be incorporated in the composite panel.

This is of particular importance when the composite panel is to be incorporated into a window of a vehicle, for example a passenger coach of a train, especially if the coach has a high glazed area. A further important advantage of the use of such polymers is that they can incorporate catalysts and/or actuators so that they may easily be polymerised in situ. The polymer can be incorporated between the two vitreous sheets in a fluid state and then polymerised. This greatly facilitates manufacture of the composite panel as compared with the use of a preformed film of highly plasticized polymer.

In the most preferred embodiments of the invention, such polymer is an acrylic resin which is polymerizable by ultra-violet radiation.

Advantageously, the material of which the intervening layer is formed has a Shore A hardness measured at 200C of not more than 50, and preferably not more than 30.

The adoption of this feature tends to promote a very efficient acoustic attenuation.

Preferably, the critical frequency of coincidence of the composite panel is 1.2 times, most preferably 1.5 times the critical frequency of coincidence of the notional monolithic vitreous sheet.

In a preferred embodiment of the invention, the polymeric material layer has viscoelastic properties such that the critical frequency of coincidence (or the lower or lowest critical frequency of coincidence if there is more than one) of the panel ["the coincidence frequency (6p) of the panel"] is greater than the critical frequency of.

coincidence of a notional monolithic vitreous sheet ["the coincidence frequency (6m) of the equivalent monolith"] which monolithic sheet is of the same shape and area as the panel and has a mass equal to the total mass of vitreous material in the panel. Preferably, the composite panel affords an acoustic attenuation Rw of at least 37dB. Such an acoustic attenuation gives considerable benefits in the comfort of various locations, and is especially useful in environments where external noise levels are rather high, such as for example in railway carriages.

A composite panel may be formed from two or more vitreous sheets which are of equal thickness, or there may be an inequality of thickness between the sheets, the latter arrangement leading to different acoustic isolation properties.

Advantageously, the second panel of the glazing unit according to the invention consists of a single unlaminated sheet of vitreous material. Such a sheet is very much less costly to produce than a composite panel.

Preferably, all the vitreous sheets of the unit have been subjected to a thermal tempering treatment.

Means for indicating the ingress of water may be incorporated in the air space between the glazing panels.

These means may be in the form of a container formed of polymeric material containing a composition comprising a desiccant such as silica gel and a humidity indicator such as cobalt chloride. The container may be formed with pins on its underside, to enable it to be retained against the spacer in use. If the sealing of the unit should fail during use, the ingress of atmospheric moisture will cause the cobalt chloride indicator to pass from a blue to a pink colour. This colour change can be used as an alarm to indicate possible failure of the unit and the need to submit the unit to further tests to determine whether repair or replacement is necessary.

According to a further aspect, the invention also provides a method of constructing the multiple glazing unit comprising the steps of: (i) positioning two vitreous material panels in faceto-face spaced apart relationship, with the gas space there-between delimited by the peripherally extending spacer, at least one portion of the first of the vitreous panels overlapping an edge of the second of the vitreous panels; (ii) positioning the support member or members to extend along at least the major part of one margin of the glazing unit to constitute means for fixing the glazing unit to a support structure; and (iii) securing the panels together, and securing the or each support member to the panels, by the cordon of resin.

The cordon of resin is preferably applied to extend at least between the spacer and each of the panels. The panels may be secured together by applying the cordon of resin in contact with at least one face of the first panel and with at least one face of the second panel.

The cordon of resin is preferably applied in contact with the overlapped edge of the second panel.

Preferably, the or each support member is constituted by a rigid frame which is positioned adjacent the second panel before the application of the resin. Thus, the method preferably comprises the additional step of positioning a rigid frame adjacent the second vitreous panel, the resin being positioned in contact with the frame to secure the vitreous panels to the frame.

This simple construction method may be carried out online under a controlled atmosphere, to ensure that the support member(s) is (are) correctly and securely bonded to the unit for fixing the unit in its intended place in a secure manner, and, at the same time, to ensure that the gas space has a sufficiently low humidity. The unit comes from the factory in a ready-to-install condition, requiring substantially no further construction on site, other than securing of the unit to the supporting structure of a building for example.

The invention will now be further described with reference to the accompanying drawings, in which: Figure 1 shows in partial cross-section a double glazing unit according to a first embodiment of the invention; Figure 2 shows in partial cross-section a double glazing unit according to a second embodiment of the invention; and Figure 3 shows in partial cross-section a double glazing unit according to a third embodiment of the invention.

Referring to Figure 1, there is shown a double glazing unit comprising two glass sheets 1, 2 positioned in faceto-face spaced apart relationship, having a gas space 3 there-between delimited by a peripherally extending spacer 4 formed of galvanised steel of 0.4 mm thickness.

The first sheet 1 constitutes the exterior sheet of the glazing unit. One portion la of the first vitreous sheet 1 overlaps an edge 2a of the second vitreous sheet 2.

The overlapping marginal portion la extends around the periphery of the composite sheet.

Layers of polyisobutylene sealant 5, 6 are positioned between the spacer 4 and each of the sheets 1, 2. The polyisobutylene used has a permeability of about 0.11 g water x mm thickness per m2 x 24 h x kPa water vapour.

A cordon of resin 9 is positioned in contact with the sealant 5, 6 between the sheets 1, 2 beyond the spacer 4 and extends to the far side of sheet 2. The resin 9 is a silicone adhesive material which exhibits, at 200C, an elongation of not more than 12.5% when subjected to a tensile stress of 0.1 MPa, as measured according to ISO 8339. The preferred silicone bonding adhesive material is "Q 3362" ex Dow Corning, having an elongation of 12.5 % when subjected to a tensile stress of 0.27 MPa, before ageing and an elongation of 12.5 % when subjected to a tensile stress of 0.2 MPa, after ageing for 21 days in water at 550C, as measured according to method A of ISO 8339. The rupture strength of this material is 1.08 MPa before ageing, and 0.92 MPa after ageing, the elongation at rupture being more than 50% and the rupture being cohesive, both before and after ageing. The resin 9 is in contact with one face of the first sheet 1 and also with both faces and the edge 2a of the second sheet 2.

A rigid frame 7 is in contact with the resin 9 to secure the vitreous sheets to the frame. The space between the vitreous sheet 2 and the upper edge of the frame 7 is filled with a silicone sealant material 10, having a low modulus of elasticity, acting to seal the glazing unit as a whole from the ingress of moisture. The silicone sealant material 10 may be "Q 33797" ex Dow Corning.

The frame 7 is provided with suitably positioned and shaped flanges 8, 8' whereby it is to be secured to the structure of a building or the like.

In use, the sealant 5, 6 provides a barrier to the penetration of water vapour into the gas space 3 while the resin 9 serves to retain the sheets 1, 2 in their face-to-face relationship.

The multiple glazing unit shown in Figure 1 is constructed as follows. Firstly, sealing tubes of polyisobutylene are disposed on the side faces of the spacer 4 to an adequate extent, the spacer is disposed along the marginal zone of one of the sheets of glass and the other sheet of glass is disposed there-over with the portion la of the first vitreous sheet 1 overlapping the edge 2a of the second vitreous sheet 2. The sheets of glass are then pressed together to squash the butyl sealant to the desired extent between the sheets of glass. In order to prevent the sides of the spacer deforming during this process, the butyl sealant may be heated to soften it. This may in particular be achieved by heating the spacer, for example by the Joule effect or by induction.The rigid frame 7 is then positioned adjacent the second vitreous sheet, the assembly at this stage being held in a suitable vice.

Thereafter, the cordon of resin 9 is applied injected into the peripherally formed space and hardened or allowed to harden. The resin 9 extends between the spacer 4 and each of the sheets, so that it is in contact with at least one face of the first sheet 1 and also with both faces and the edge of the second sheet 2.

Referring to Figure 2, there is shown a double glazing unit comprising two glass sheets 21, 22 positioned in face-to-face spaced apart relationship, having a dry air gas space 23 there-between delimited by a peripherally extending spacer 24. The cross-section of the spacer 24 has a flared "U" shape, comprising two flared arm portions interconnected by a base portion. The crosssection is open to the gas space 23. Layers of sealant 25, 26 are positioned respectively between the spacer 24 and each of the sheets 21, 22. A cordon of polysulphide or silicone resin 29 is positioned in contact with the sealant 25, 26 between each of the sheets 21, 22 and the spacer 24 and between the sheets 21, 22 beyond the spacer 24.

A rigid frame 27 is in contact with the resin 29 to secure the vitreous sheets to the frame. In this embodiment, there is no space between the vitreous sheet 22 and the upper edge of the frame 27. The frame 27 is provided with suitably positioned and shaped flanges 28, 28' whereby it is to be secured to the structure of a building or the like.

Figure 3 shows a glazing unit in which one panel comprises a composite glazing panel having a pair of vitreous sheets 31, 32 with an intervening layer 33 of acrylic polymer sandwiched there-between. The first sheet 31 is formed of thermally tempered glass having a thickness of 6 mm and carrying a solar screening coating of STOPSOL (Trade Mark), on the internal face thereof.

The second sheet 32 is formed of thermally tempered glass having a thickness of 5 mm and carrying a low emissivity coating. A low emissivity coating is provided on that face of the sheet 32 which is disposed remote from the sheet 31. The first sheet 31 constitutes the exterior sheet of the glazing unit. One portion 31a of the first vitreous sheet 1 overlaps an edge of the second vitreous sheet 32. It is a preferred construction that the overlapping portion 31a extends around the whole periphery of the composite panel.

The acrylic polymer layer 33 has viscoelastic properties such that the critical frequency of coincidence of the panel is greater than the critical frequency of coincidence of a notional monolithic vitreous sheet which is of the same shape and area as the panel and has a mass equal to the total mass of vitreous material in the panel. A suitable acrylic polymer is UVEKOL (Trade Mark) ex UCB SA, of B-1620 Drogenbos, Belgium.

The glazing unit shown in Figure 3 is in the form of a double-glazed unit including a second glazing panel 37, formed of 5 mm thermally tempered glass, positioned in face-to-face relationship to sheet 32 of the composite panel, and spaced therefrom to provide an air space 36 of 12 mm. A "Swiggle Strip" spacer 38 assists in positioning of the second glazing sheet 37. The spacer acts additionally as a moisture barrier.

A silicone bonding adhesive resin 39 is in contact with each vitreous sheet 31, 32, to the extent of about 8 mm from the peripheral edge thereof. The silicone bonding adhesive resin 39 serves to prevent delamination of the composite panel, even after ageing as a result of mechanical or climatic conditions in use.

The resin 39 is in contact with one face of the first sheet 31 and also with both faces and an edge of the second sheet 37.

The glazing unit according to Figure 3 further comprises a rigid aluminium profile frame 42 and corner plates 43.

The space between the vitreous sheet 37 and the upper edge of the frame 42 is filled with a silicone sealant material 41, having a low modulus of elasticity, acting to seal the glazing unit as a whole from the ingress of moisture.

The method of constructing the glazing unit according to Figure 3 comprises the following steps. Firstly, the pair of vitreous sheets 31, 32 are positioned in face-toface spaced relationship to each other. A ribbon 34 of butyl sealing material having a width of 8 mm is disposed between the sheets 31 and 32 at a distance of approximately 8 mm from the peripheral edges of the sheet 31. This ribbon is formed by placing a cylindrical cordon of the butyl sealing material on one of the vitreous sheets and squeezing the cordon into a ribbon of the specified width by pressing the two sheets together.The ribbon 34 is continuous save for two interruptions (not shown) to enable, respectively, the evacuation of the space between the vitreous sheets and the injection into that space of an acrylic polymer precursor, the ribbon delimiting the area occupied by the polymeric material in the composite panel. After the injection of the precursor, the interruption in the ribbon of sealing material is closed by the provision of further sealing material. The acrylic polymer precursor is then caused to polymerise to the polymer by exposure to ultra-violet radiation.

The next step of the process is the positioning of the spacer 38, optionally followed by the positioning of a container formed of polymeric material containing a composition comprising a silica gel desiccant and cobalt chloride. The container (not shown), formed with pins on its underside, is retained against the spacer 38. If the sealing of the unit should fail during use, the ingress of atmospheric moisture will cause the cobalt chloride indicator to pass from a blue to a pink colour.

This colour change can be used as an alarm to indicate possible failure of the unit and the need to submit the unit to further tests to determine whether repair or replacement is necessary.

The second glazing panel 37 is put in place and the frame 42 is positioned with its upper edge adjacent the sheet 37. The silicone bonding resin 39 is then injected so that the resin 39 is in contact with at least one face of the first sheet 31 and of the second sheet 32 and also with both faces and the edge 37a of the second sheet 37.

The corner plates 43 are then disposed against the silicone bonding resin 39.

The frame 42 of the glazing unit is secured (by means not shown) to the chassis of a vehicle, for example in a flush manner with the bodywork of a railway carriage or to the structure of a building.

Claims (21)

1. A multiple glazing unit comprising at least two vitreous material panels positioned in face-to-face spaced apart relationship, having a gas space (3; 23; 36) there-between delimited by a peripherally extending spacer (4; 24; 38), and a cordon of resin (9; 29; 39) securing said panels together, wherein: - at least one portion (la; 21a; 31a) of the first of said panels (1; 21; 31) overlaps an edge (2a; 22a; 37a) of the second of said panels (2; 22; 37); and - at least one support member (7; 27; 42) extending along at least the major part of one margin of the glazing unit is secured to said vitreous panels by said resin (9; 29; 39) to constitute means for fixing the glazing unit to a support structure.

2. A glazing unit according to claim 1, wherein said cordon of resin (9; 29; 39) extends at least between said spacer (4; 24; 38) and each of said panels.

3. A glazing unit according to claim 1 or 2, wherein said at least one support member is constituted by a rigid frame (7; 27; 42).

4. A glazing unit according to any preceding claim, wherein said resin (9; 29; 39) is in contact with at least one face of the first panel (1; 21; 31) and with at least one face of the second panel (2; 22; 37).

5. A glazing unit according to any preceding claim, wherein said cordon of resin (9; 29; 39) is in contact with the overlapped edge (2a; 22a; 37a) of the second panel (2; 22; 37).

6. A glazing unit according to any preceding claim, wherein said overlapping marginal portion (la; 21a; 31a) extends around the periphery of said unit.

7. A glazing unit according to any preceding claim, wherein said resin (9; 29; 39) is an adhesive material which exhibits, at 200C, an elongation of not more than 12.5% when subjected to a tensile stress of 0.1 MPa, as measured according to ISO 8339.

8. A glazing unit according to claim 7, wherein said adhesive material exhibits, at 200C, an elongation of not more than 12.5% when subjected to a tensile stress of 0.14 MPa.

9. A glazing unit according to claim 7 or 8, wherein said adhesive material exhibits, at 200C, an elongation of not more than 12.5% when subjected to a tensile stress of 0.1 MPa after ageing for 500 hours in water at 550C.

10. A glazing unit according any one of claims 7 to 9, wherein said adhesive material exhibits said elongation of not more than 12.5% when subjected to a tensile stress of 0.14 MPa after ageing in water for 1000 hours at 450C.

11. A glazing unit according to any one of claims 7 to 10, wherein the adhesive material exhibits a rupture strength at 200C of more than 0.70 MPa and a deformation at rupture of greater than 50%.

12. A glazing unit according to any preceding claim, wherein said resin (9; 29; 39) is selected from silicone adhesive materials.

13. A glazing unit according to any preceding claim, wherein one of said vitreous panels is constituted by a composite glazing panel having a pair of vitreous sheets (31, 32) adhered to an intervening layer (33) of polymeric material sandwiched there-between.

14. A glazing unit according to claim 13, wherein the intervening polymeric layer (33) is selected from polyesters, vinyl polymers, epoxy resins, and acrylic resins.

15. A glazing unit according to any preceding claim, wherein layers of sealant (5, 6; 25, 26) are positioned between said spacer (4; 24; 38) and each of said panels.

16. A glazed structure, at least one facade of which incorporates a plurality of glazing units as claimed in any one of claims 1 to 15.

17. A method of constructing a multiple glazing unit comprising the steps of: (i) positioning two vitreous material panels in faceto-face spaced apart relationship, with a gas space (3; 23; 36) there-between delimited by a peripherally extending spacer (4; 24; 38), at least one portion (la; 21a; 31a) of the first of said vitreous panels (1; 21; 31) overlapping an edge (2a; 22a; 37a) of the second of said vitreous panels (2; 22; 37); (ii) positioning at least one support member (7; 27; 42) to extend along at least the major part of one margin of the glazing unit to constitute means for fixing the glazing unit to a support structure; and (iii) securing said panels together, and securing said at least one support member to said panels, by means of a cordon of resin (9; 29; 39).

18. A method according to claim 17, wherein said cordon of resin (9; 29; 39) is applied to extend at least between said spacer (4; 24; 38) and each of said panels.

19. A method according to claim 17 or 18, wherein said panels are secured together by applying said cordon of resin (9; 29; 39) in contact with at least one face of the first panel (1; 21; 31) and with at least one face of the second panel (2; 22; 37).

20. A method according to any one of claims 17 to 19, wherein said cordon of resin (9; 29; 39) is applied in contact with said edge (2a; 22a; 37a) of the second panel (2; 22; 37).

21. A method according to any one of claims 17 to 20, wherein said at least one support member is constituted by a rigid frame which is positioned adjacent said second panel before the application of said resin.